The unidentified victim was shot three times at 9:45 a.m. when two men drove up and started firing at two men at Fulton and Steiner streets, said San Franicsco police Sgt. Neville Gittens. The two victims ran but were followed by the gunmen and more shots were fired at Grove and Steiner streets.

Mirkarimi, who was jogging in the area, heard gunfire, reported what he saw to police and got into a patrol car to help them locate the suspects, authorities said. Two men were arrested later Friday.

"Up until this incident today, it's been one of the safest summers we have had in a long, long time, in the Western Addition," said Mirkarimi, who was reluctant to talk about his role in the arrest.

Police said they have a policy against identifying witnesses but thanked the several people who came forward for assisting officers in making the arrest.